1    package javassist.sample.duplicate; 
2     
3    import javassist.reflect.*; 
4     
5    public class DuplicatedObject extends Metaobject { 
6        private DuplicatedObject backup; 
7     
8        // if a base-level object is created, this metaobject creates 
9        // a copy of the base-level object. 
10    
11       public DuplicatedObject(Object self, Object[] args) { 
12           super(self, args); 
13           ClassMetaobject clazz = getClassMetaobject(); 
14           if (clazz.isInstance(args[0])) 
15               backup = null;  // self is a backup object. 
16           else { 
17               Object[] args2 = new Object[1]; 
18               args2[0] = self; 
19               try { 
20                   Metalevel m = (Metalevel) clazz.newInstance(args2); 
21                   backup = (DuplicatedObject) m._getMetaobject(); 
22               } catch (CannotCreateException e) { 
23                   backup = null; 
24               } 
25           } 
26       } 
27    
28       public Object trapMethodcall(int identifier, Object[] args) 
29               throws Throwable { 
30           Object obj = super.trapMethodcall(identifier, args); 
31           if (backup != null) 
32               backup.trapMethodcall(identifier, args); 
33    
34           return obj; 
35       } 
36   } 
37